JPS5947553A - Continuous type variable ratio transmission control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission system for a continuously variable transmission (CVT), for example for use in a motor vehicle.

Continuously variable transmissions are well known in the art.

Exists in various configurations. Generally, ratio control systems for such transmissions use an inner servo loop (θ) to vary the speed or torque ratio between the input and output shafts of the transmission according to the position of an adjustable control member.
o 1oop) 'a: Contains. Outer servo loop (
outer 5erv.

1oop) adjusts the position of the control member 11i so that the transmission ratio changes in such a way that the actual ratio corresponds to the desired ratio determined according to the input torque or speed command.
i do

This crest-type ratio control system is described in U.S. Patent No. 4.291.
．． No. 594 (Bauao4n). In this conventional control system, the change in ratio control member σ) as a function of time is proportional to the difference between the actual and desired speed ratio between the transmission input and output shafts.

In a system of the general type described above, the gains or transfer functions of the inner and outer τpo-loops have a shifting response so that the overall gain (transfer function) of the ratio control system satisfies the drivability criterion or the stability criterion. repose
). The overall gain is therefore typically a compromise between driveability, which requires a fast response, and stability, which requires a slow response.

Since the control forces required in the ratio changing mechanism are relatively high, the inner servo loop described above is typically implemented with hydraulic or hydrodynamic control. As a result, the gain of the inner servo loop does not change easily and is non-constant over a range of transmission ratios.
, nt). According to conventional servo control technology, the gain of the outer servo loop is limited by the maximum gain of the inner servo loop to provide a stable overall response, P = -4°, and the stable response reduces the driveability. It is considered undesirable to rely on such techniques since they can only be obtained through sacrifice.

The present invention ensures that the overall gain of the ratio control system provides a stable response consistent with 1:4 driveability.

θ) for a continuously variable ratio transmission;

To this end, a continuously variable ratio transmission control system according to the present invention is constructed such that the response of the inner loop is such that the rate of change of the speed ratio with respect to the position of the actuating member is a non-constant function of the actual speed ratio. (non-constant func
tion).

When the ratio error is greater than or equal to a predetermined value L, the rate adjusting means adjusts the adjustment rate of the actuating member so that the rate of change in the position of the actuating member with respect to time is a direct release of the ratio error, and eliminates the error.
Further adjustments below this level may jeopardize the stability of the system in view of the non-constant response of the inner servo loop.A relatively rapid reduction to said predetermined value provides an overall system response with a satisfactory transition window. and furthermore, when the ratio error is less than or equal to the predetermined value, the rate adjusting means causes the rate of change of the actuating member position with respect to time to be a constant function of the actual speed ratio and inverse to the non-constant function of the inner loop. By adjusting the rate of adjustment of the actuating member so as to provide a substantially constant rate of change of speed ratio with respect to time for all actual speed ratio values and causing said error to decrease relatively slowly, The present invention is characterized in that the speed ratio corresponds to a desired speed ratio in a stable manner.

Therefore, in such a control system, the gain of the outer servo loop provides a fast transitional response when the difference between the actual ratio ζ and the desired ratio is such that the driveability is the primary control object. When the difference from the desired ratio is such that stability is the primary control object, it is controlled to provide an overall control system gain that supports slow transient response.

The outer servo loop gain, which provides a slow transitional response, is such that even though the inner servo loop gain varies as a function of transmission ratio, the rate of change of ratio is essentially constant with respect to time for all transmission ratios. , may be related to the inner servo loop gain.

In a particular arrangement of the control system according to the invention:
Between the actual speed ratio and the desired speed ratio, above which the primary controlled object has a response speed consistent with satisfactory drivability; A reference ratio error is established such that is a stable response with limited overshoot.

If the difference between the actual speed ratio and the desired speed ratio □speed ratio error □ is less than or equal to the reference speed ratio error, the gain of the outer servo loop is the non-constant gain of the inner servo loop with respect to the actual speed ratio. is controlled as an inverse function of In this way, even though the gain of the inner servo loop varies as a function of speed ratio, the composite response provides a nearly constant rate of change of ratio with respect to time for all speed ratio values. A constant rate of change of this ratio is chosen such that the actual speed ratio has a limited overshoot for the desired speed ratio so that the overall response is stable for all speed ratio values. It will be done. Such operation is designated as a slow or steady mode of operation and provides a repeatable response throughout a range of transmission ratios.

In a first embodiment of the invention, the gain of the outer servo loop is a function of the speed ratio error when the speed ratio error is at or above the reference speed ratio error so that the overall response provides a satisfactory transition window. controlled as

In a second embodiment of the invention, the gain of the outer servo loop is controlled as a function of both the speed ratio error and the actual speed ratio when the speed ratio error is at or above the reference speed ratio error.

Unlike the first embodiment, the second embodiment compensates for the non-constant gain of the inner surfolub for all values of speed ratio error.

In either case, the -order control object is the drivability or satisfactory transition window, and operation under such conditions is designated as a fast mode of operation.

Now, in FIG. 1, reference numeral 10 indicates engine 12;
A motor vehicle drive train consisting of a forward/reverse clutch mechanism 14 and a continuously variable ratio transmission 16 is shown. The engine output shaft 18 drives a transmission input shaft 20 via a clutch mechanism 14, and the transmission output shaft 22 is connected in a known manner to the drive wheels of a differential or armament (not shown).

Reference numeral 24 designates an engine throttle consisting of a butterfly valve 26 pivoted within housing 30 about pin 28 to control the power output of engine 12. The throttle 24 is controlled in a known manner via a suitable linkage mechanism (not shown), for example by an accelerator pedal (not shown). A transducer 52, such as a rotary potentiometer, is responsive to the position of the throttle 24, as indicated by the dashed line 4, and the output of the transducer 24 indicating the throttle position is input to the controller 5 via line 36.

The transducer rollers 8, 40, 42 are connected to the shafts 18, 2, respectively.
0,22σ What rotation speed does it respond to?

The output of such a transducer is connected as an input to the control section 55 via a line 44.46.48. Each transducer 38, 40j42 is a known device such as a variable reluctance magnetic speed pickup having a magnetic circuit intermittently cooperating with the teeth of a wheel or gear rotatably coupled to the respective shaft. It may be. The output of transducer 38 therefore indicates the velocity of shaft 18, and this velocity is designated as Ne. The output of transducer 40 indicates the velocity of shaft 20, and this velocity is designated YN□. The output of transducer 42 indicates the speed of shaft 22 and this speed is 7N.
Indicated by 0.

Reference numeral 50 indicates the manually operated gear in the passenger compartment of the vehicle.
Displays a range selector, movable to one of five designated positions. Including jlJ Goreno\shi52. The position of the range selector 50 is similar to that seen in conventional automobiles.
Similarly, 9th position "P" represents parking 2, 9th position IRJ represents reverse, 1st position INJ represents neutral, 9th position "D" represents drive name, 1st position "G" represents grade forward direction that requires high output torque Indicates the driving range.

Transducer 54 is responsive to movement of control lever 52, as shown by dashed line 56, and generates an output signal indicative of the range of positions to which control lever 52 is directed. This output is on line 58
It is connected as an input to the control section 5 through (.

The control section 6.5 operates in response to each of the above inputs to provide output control signals for shifting jljA16 and clutch 14σ. The control signals for transmission 16 include an actuator control signal on output line 60 for controlling the position of the ratio control member and a pressure control signal on output line 62 for regulating the working fluid pressure within transmission 16. Including signal resistance. The control signals for clutch 14 include an actuator control signal on output line 64 to control clutch engagement and disengagement, and a single actuator control signal on output line 64 to provide increased cooling of the clutch friction surfaces when the slip between the clutch friction surfaces exceeds a reference value. and a pump control signal on the output line 66 of the pump.

FIG. 2 shows a transmission 16. Clutch 14 and control section 6
5 is shown in some detail.

The various lines and devices depicted in FIGS. 1 and 2 are labeled with corresponding reference numerals. Therefore, the speed signal N. , N□, No.

The throttle signal and manual range and selector signals are applied to the control unit 65 via lines 44, 46, 48, 36 and 58, respectively.

Further, the control unit output line 60 , 62 is connected to the transmission 16 , and the control unit output line 64 , 66 is connected to the clutch 14 . For simplicity, engine 12. The shaft 18 and the transducer filter 2j 8.54 are not shown.

The transmission 16 has a manual lift 0 connected to a transmission input shaft 20 so as to be rotatable integrally therewith.

It consists of a transmission output shaft 22 and an output boolean 2 rotatably connected thereto. A belt 74 is supported on the inner conical surfaces of pulleys 70 and 72. The pulley half 76 of the input boolean 0 is axially movable relative to the pulley half 78, and the pulley half 76 of the output boolean 2 is movable in the axial direction relative to the pulley half 78.
0 is movable in the axial direction with respect to the boob half 82.

A regulated control pressure obtained from a fluid pressure source (not shown) forces pulley half 80 toward pulley half 82;
The higher control pressure in gland 1 84 is applied via valve 86 and line 88 to a piston mechanism (not shown) in input boolean 0 to move pulley half 76 relative to pulley half 78. Movement of pulley half 76 relative to pulley half 78 in response to control pressure in line 88 increases or decreases the effective diameter of input bolief 0;
This provides additional movement of the pulley half 80 in relation to the half rest 82 to increase or decrease the effective diameter of the output boliet 2. ■
Belt 74 is supported at the effective diameters of input bolief 0 and output bolief 2. In this way, movement of the pulley half 7B with respect to the pulley half 78 continuously or steplessly changes the speed or torque ratio between the transmission input shaft 20 and the transmission output shaft 22. It is controlled in a way that forces you to do so.

A lever 90 is pivotally mounted on the valve 92 at a point 94. One end of lever 90 abuts against the inner conical surface of pulley half 76 and the other end of lever 90 abuts against shaft 96 of linear actuator 98. Valve stem 92 is depicted in the zero (steady state) position. Movement of the valve stem 92 from the zero position due to movement of either the pulley half 76 or the actuator shaft 9 causes the valve 86 to be moved by the line 8 to cause the pulley half 76 to move in order to return the valve stem 92 to the zero position.
Change the pressure inside 8.

In view of the above, the transmission output shaft 22 and the transmission input shaft 20
The speed ratio (qo/rq, ) between the It will be appreciated that the ratio may be varied steplessly over the range.

A more detailed explanation of the above-mentioned transmission ratio control mechanism is given in Japanese Patent Application Laid-open No. 57-107459, in the name of the applicant.

Transmission 16 further includes a pressure regulating valve 100.

This, in conjunction with the pressure sources described above, generates regulated fluid pressures for the various hydraulic transmission lines, such as line 84. The output of pressure A regulator 100 is typically referred to as transmission line pressure, which is controlled by throttle position and pressure to prevent belt 74 from slipping on pulleys 70 and 72 under varying load conditions. It is made to vary as a function of speed ratio. In the illustrated embodiment, pressure regulating valve 100 includes a solenoid actuated valve member that regulates transmission line pressure by a pulse width modulated (p w M ) energizing signal from p WIA driver 102 via line 62 . (not shown).

A linear actuator 11 serves as a control element within the clutch mechanism 14.
0 and a lubrication pump 112 driven by an electric motor. Shaft 114 of actuator 110 moves in a linear direction in response to energization of actuator 11Q via line 64, and shaft 114 establishes a driving connection between engine output shaft 18 and transmission input shaft 2o. The clutch elements (not shown) are adapted to move one clutch element (not shown) relative to the other. Lubrication pump 112
is energized via line 66 to lubricate the clutch surfaces whenever the slip between the clutch elements of the clutch mechanism exceeds a reference value.

The invention is independent of the exact nature of linear actuators 98 and 11o. However, for purposes of this description, one actuator 98
Assume that 1 and 110 are known stepper motors requiring linear output shaft movement.

In the illustrated embodiment, the control unit 35 includes a microprocessor (+apU) 120 and one peripheral interface adapter (
PI l-) 122, and an analog-to-digital converter [A/D] 124.

A microprocessor-based controller consisting of timers 12'6 and 128. MPU 120 has an address and control bus 130 and a bidirectional data bus.
162 buses communicate with the above components in a known manner.

Clock 134 is connected to MPU 12 via line 166 for timing the operation and interaction of various control elements.
0 is given a high frequency clock pulse train. MPU12D'
a? Each element included may be any of a number of known commercially available devices. For example, MPU120 is MC68
It's 02, PIA12!2 is MC682,1.

Timers 126 and 128 may be Mc684o.

All of these are manufactured by Motorola Semiconductor Products. Analog-to-digital converter 124 may be an ADC8D8 manufactured by Analog Devices. Analog inputs such as the throttle signal on line 56 are input to the A/Di converter 124, while digital input signals such as the manual selector signal on line 5B are input to the PIA 122. is input. The speed signals on the lines 44, 46, 48 are each input in a known manner into a counter contained within a counter block designated by the reference numeral 138.

Timers 126 and 128 are programmable and receive clock signals, such as from clock 134, to perform various timing and counting functions. timer 12
6 and 128 are connected to MPU 12 via address and control bus 130 and data bus 162, respectively.
] Contains six separate timer modules controlled by: The output of the counter in counter block 168 is input to timer 126 via line 169140.142. Timer 126 converts the output signal from counter 168 into a digital representation of the rotational speed of the respective shaft, as described below.

This eliminates the effects that occur on the interrupt signal line 127 for the MPU 120. Timer 128 serves to generate actuation signals for lubrication pump 112 and PWIV1 driver 102 on lines 1'5DJ6 and 154, respectively, as described below. According to a preferred embodiment, MPU 120 includes read-only (ROM) and random access (RA rt ) type storage elements.

As is well known, random access memory is used for temporary storage of information such as input signal values, and read-only memory is used for permanent storage of data tables and program instructions.

The output command for linear actuators 98 and 110 is line 1
62 and 1642 to drive circuit 160. Driver 160 may be a conventional step motor repeater or driver and operates to energize actuators 98 and 110'Y via lines 60 and 64 according to actuator commands on lines 162 and 164.

FIG. 3 is a control system diagram for the control section 65 and the ratio control elements of the transmission 16, showing each element consisting of the inner and outer servo loops. It will be appreciated that this is a schematic diagram of a system. The inner servo loop is designated by reference numeral 170 and the outer servo loop is designated by reference numeral 172.

Function generator 174 generates a desired speed ratio on line 176 for transmission 16 in accordance with the following parameters: throttle position on line 36, transmission output speed on line 48, and manual selector position on line 58. Such IA numbers are implemented by MPU 120 via look-up-takes or other known function generation mechanisms.

Outer servo loop 172 consists essentially of the following: namely, a linear actuator 98, a conversion section 180 for determining the actual speed ratio, and a summing link for distinguishing between the actual speed ratio and the desired speed ratio to form a speed ratio error signal E. logic and drive circuitry 184 for orthodontically energizing section 9B. Therefore, the flocks 180-184 are implemented in the control unit 65.

Block 98 is physically contained within transmission 16.

Inner loop 170 consists essentially of: That is, block 1 includes a ratio control element indicated by block 190, including valve 86 and the piston mechanism described in FIG.
92 and a valve stem 92 for determining the position error P2p between the actual position of the pulley half 76 and the position corresponding to the linear axis position of the actuator 98; and a summing connecting element. Therefore.

The valleys of the inner servo loop element are housed within the transmission 16.

The transmission drive line elements are directly controlled by the inner servo loop 170. Such elements are indicated by block 196;
Shafts 20, 22. Boo 1J70, 72 and V belt 74
including.

Inner and outer servo loops 170 and 172 together act to establish a transmission speed ratio that corresponds to the desired speed ratio determined by function generator 74. The inner servo loop 170 controls transmission elements 70-927a1'' to establish a transmission speed ratio that corresponds to the linear position of the actuator output shaft 96. Therefore, the gain of the inner servo loop 170 is equal to the unit change in actuator shaft position. The speed ratio change □ may be expressed as a ratio of 7 inches □, for example. Such gains are not easily modified and, as discussed with respect to FIGS. 4 and 5, typically vary from the actual speed ratio given. It is a constant function.

The outer servo loop controls actuator 95 to establish the actuator output shaft position corresponding to the desired speed ratio. Outer servo loop 172 also controls the rate of change of position of the actuator. Strictly speaking, the direction of movement is determined depending on whether the actual ratio is greater than or less than the desired speed ratio.

The rate of change of position is varied to meet stability and driveability criteria. Therefore outer servo loop 1
A gain of 72 is expressed in terms of movement per unit time, such as inches or steps per second.

The overall gain of the control system is the product of the gain of the inner servo loop 170 and the gain of the outer servo loop 172. Using the gain units described above, it can be seen that the total gain can be expressed as a ratio per second.

The rate per second and the output parameters directly affect the stability of the control system as well as the dynamic driveability experienced by the vehicle floor. The present invention is directed to a control scheme for the outer servo loop 172 to provide a stable overall response at the cost of a rate of change in terms of time at the cost of drivability.

In FIG. 4, the 8 curve 198 is the speed ratio (N
9] depicts an experimentally determined relationship between the linear position of the actuator output shaft 96. The movement or position of axis 96 is shown in inches, where zero inches corresponds to a fully retracted position and 0.75 inches (19,
051EI) corresponds to a fully advanced position. axis 96
The change in velocity ratio for a given change in position represents the gain of inner servo loop 170 and is given by the slope of curve 198.

For example, the speed ratio is 0.6 RPM as shown at point A.
/'RPM, the gain of the inner servo loop 170 is approximately 1.5 ratio/inch.

The speed ratio is 2.10RPkfr- as shown at point B.
/RPM, the gain is approximately 7.3 ratio/inch. Therefore, the gain of the inner loop 170 is equal to the speed ratio of 2.1.
When it is at a high value such as ORPM/RPM, the speed ratio is 0.6 RPM/p.

This will be greater than when it is at a low value such as PM. Alternatively, the inner loop gain change may be described as a function of the linear position of the actuator shaft 96.

The change in gain due to a 7 inch ratio of the inner servo loop 170 is shown in FIG. 5 as a r8Ij number of actual speed ratios. Fourth
The graph depicted in FIG. 5 and the transmission 11 described in the published patent application and FIG.
4, it will be understood that the relationship .rho..rho. may not be the same as for other continuously variable transmission mechanisms. but.

Transmission 16 appears to be typical of most transmission mechanisms in that its inner loop gain is non-constant over a given speed ratio range. That is, different gear shift 4
(Although the gain of the ! structure is probably different from the relationship shown in Figure 5.

The gain for such different transmission mechanisms will also likely be non-constant as a function of the actual speed ratio.

In FIG. 6, the desired rate of change in speed ratio (total gain) over one hour is plotted as a function of the magnitude of the speed ratio error. As shown above, the overall gain due to the 7s ratio directly affects stability and drivability criteria. Generally speaking, a slow overall gain is required to provide a stable response, whereas a fast overall gain is required to provide adequate response speed for drivability problems. The control problem is further compounded by the non-constant nature of the inner loop gain as depicted in FIG.

In order to solve such inherent difficulties, the present invention establishes a reference speed ratio error above which the primary controlled object exhibits response speed (drivability) and below which the primary controlled object exhibits response stability. According to the first embodiment, such reference speed ratio error is 0.10R''PM/RPM and is indicated by the trap line 200°. According to Example 2, such reference speed ratio error is 0.05 RPM/RP
M and is indicated by a dashed line 200'. Therefore, the desired response curve in FIG. 6 is region A for speed ratio errors smaller than the reference error and region B for speed ratio errors larger than the reference error.
It is divided into The broken line 205 has a standard error of 0.05 R.
The desired overall gain for the second example is P M / R P M 2 .

In the Craftsman, stability is the primary control and the desired overall gain should be chosen such that the actual speed ratio corresponds to the desired speed ratio with an acceptably small amount of overshoot. In the illustrated embodiment, such gain is approximately 0
It is constant at 8 ratio/sec. In region B, the response speed or drivability is the primary control side object, the gain therein is chosen according to the drivability criterion, and the transmission mechanism becomes the limiting factor for large ratio errors. In the illustrated embodiment, the gain in region B varies as a function of the direct ratio error magnitude to about 1.
Limited at 0 ratio/sec.

The reference ratio error indicated by a200 and 2 Q O' and 0.
The desired gain in region A of .08 ratio/sec is determined theoretically to satisfy the desired stability given the driveability response of region B.

As will become clear later, the second embodiment differs from the first embodiment.
The improved response of the embodiment allows its reference ratio error to be set to a lower value (0,05RPM/RPM) than in the first embodiment (0,10RPlvi/RPlt). .

According to an important aspect of the invention, inner servo loop 170
The non-constant gain of is also considered in the generation of the outer servo loop 172 gain.

In a first embodiment, the gain of the outer servo loop is varied according to the actual speed ratio in region A to provide the desired stability by compensating for the non-constant inner loop gain, and the speed ratio error in region B is increased. It is made to change according to the exact conditions. In a second embodiment of the invention, the gain of the outer servo loop 172 is varied according to the actual speed ratio in region A to provide the desired stability, and the magnitude of the speed ratio error in region B and the actual speed ratio. to compensate for the non-constant inner loop gain over the entire range of speed ratio errors.

The first embodiment is shown graphically in FIGS. 7 to 10, and the second embodiment
Example 7 is shown in graphs in FIGS. 11 to 13. In case of misalignment, 9 actuators 98 are used as step motors 41
11'i't, the outer servo loop gain is expressed by step 717 seconds. 1 step is actuator III
Since it corresponds to the specified linear movement of III96, the gain ('!.

It may equally be expressed in 7 seconds inches or 7 seconds centimeters.

FIG. 9 depicts the gain of the outer servo loop according to Step 717 as a function of velocity ratio error i for regions A and B according to the first embodiment of the invention. As in the case of FIG. 6, the sensor 200 separates the speed ratio errors in region A and region B.

In region B, the outer loop gain varies as a sole function of speed ratio error, whereas in region A, the outer loop gain varies as a sole function of speed ratio. Therefore, the ninth
The outer loop gain in the figure is plotted as a constant function of speed ratio error for area A, where the various curves in area A are associated with specified speed ratio values.

Therefore, the 9 curve 210 is 0.3 ORP M − / RP
1 curve 212 in relation to the speed ratio value of M is 0.64 RPi
1 curve 214 is 1 in relation to the speed ratio value of A/RPM.
．． 28 RPM/RPM is related to the speed j inverse ratio value.

Curve 216 is associated with a velocity ratio value of 1.92 R,p+a/np], a.

FIG. 7 shows the gain of the outer servo loop in the first embodiment of the present invention 5.
) Step 71 as a function of speed ratio for area A according to three examples.
It was drawn in 7 seconds.

Comparing FIG. 5 and FIG. 7, it can be seen that in region A, the outer loop gain has an inverse relationship to the inner loop gain. In addition, as can be seen in Figure 8, the magnitude of the outer loop gain is < O,OS as depicted in area A of Figure 6.
The magnitude of the inner loop gain is chosen relative to the magnitude of the inner loop gain to achieve a nearly constant total gain corresponding to a desired total gain in ratio/sec.

FIG. 10 shows the ratio of the total gain to 7 as the number of the first embodiment of the present invention.
There are some drawn in seconds. As in Figure 6, + +'ii
20 For A, the overall gain does not liquefy as a function of speed ratio error and is therefore depicted in FIG. 10 as a constant 1εJ number of speed ratio errors. In region B, the total gain is plotted as a family of curves because the outer fll loop gain for ratio error in region B does not compensate the total gain for the constant gain of the inner servo loop. Therefore, the group of seven curves drawn in area B of Figure 10 is specific.
t is related to the speed ratio value. For example, 1 curve 260 is 2
．． 9 songs related to the speed ratio value of ORPM/RPM
W22 filter 2 is connected to the speed ratio value of 1.5 RP Jt / RP M.

Curve 234 is 1. 9 curve 266 associated with the speed ratio value of ORP M,/RPM is 0.5 RPM/R
It is related to the PM velocity ratio value. Although only four such curves are shown here, it will be understood that these curves are only representative and that other curves may be constructed for any given speed ratio.

Also shown in FIG. 10 is a dashed curve 240 corresponding to the desired overall gain depicted in FIG. As can be seen in FIG. 10, the non-constant gain of the inner servo loop is compensated for the speed ratio error in region A so that the total gain in region A lies directly on the desired total gain value a 240. On the other hand, since the overall gain in region B is non-constant and the 11i11 servo loop gain is not compensated for, the desired gain curve 240
It is different from. Therefore.

The non-constant gain of the inner servo loop with respect to the speed ratio is also in region B.
It appears in the total gain in . Although such changes in overall gain as a function of speed ratio are generally undesirable,9 the present invention provides, in accordance with one aspect thereof, that compensation for such non-constant gain is relatively small, such as in region A where stability is the primary control object. It is recognized that speed ratio error is most important. Area B where response speed is the primary control target
For relatively large speed ratio errors such as , the overall gain, change in speed ratio is not significant and does not significantly affect the drivability of the vehicle.

FIG. 8 shows the total gain for speed ratio error in region A as a function of speed ratio. Curve 242 represents the desired overall gain. The vertical gain scale in FIG. 8 has been greatly expanded to show the deviation between the actual gain curve and the desired 11lJ gain curve; the deviation is so small that the total gain is 0.08 steps/ It is observed as almost constant in seconds.

Therefore, since the outer servo loop gain depicted in Figure 1 compensates the total gain for the non-constant inner servo loop gain depicted in Figure 5, the total gain is equal to the speed ratio σ and the total j ratio. 1. Almost constant over the range. By C.

Provides the desired stability.

The second embodiment of the present invention differs from the first embodiment described above in that the overall gain of the ratio control system is compensated for non-constant inner loop gain over the entire range of speed ratios. Ru.

Similar to the first embodiment, the outer loop gain for relatively small speed ratio errors, such as in region A, varies strictly as a function of the actual speed ratio. The gain of fighting is the 12th
7 and corresponds to the outer loop gain according to the first embodiment depicted in FIG. For relatively large speed ratio error magnitudes, such as in region B, the outer loop gain varies with both speed ratio and ratio error magnitude. Such gains are depicted in FIG.

Corresponds to the outer loop gain according to the first embodiment depicted in FIG. FIG. 13 shows the overall gain JT,l at a ratio of 2 to 7/sec for the second embodiment of the invention, which corresponds to the overall gain according to the first embodiment depicted in FIG. Due to the increased stability of the second real example given by the compensation of the inner loop gain for a larger speed ratio error than in region B, the reference speed ratio error for defining regions A and B'& is as shown in FIG. And as shown by the broken line 200' in FIG. 13, it is lowered to <: 0.05 RPM/RPM.

Turning now to FIG. 11, the outer loop ori gain due to step 7 seconds is plotted as a function of speed ratio error for regions A and B according to a second embodiment of the invention. This gain is −
jr, each curve being associated with a specified speed ratio value. In other words, 1 song section 250 is 0, 6
4 Related to the speed ratio value of RP M 7/RP M.

Curve 252 relates to a speed ratio value of 1.28 RPM/RPM; curve 254 relates to a speed ratio value of 1.92 RPM/RPM.
9 curve 256 is 255RPM/
It is related to the speed ratio value of RP rt.

As discussed above with respect to FIGS. 9 and 10, it will be appreciated that such curves are representative only and that for any speed ratio value a different curve may be constructed. 0.64
For low speed ratio values such as RPM, /RPM (+), the outer loop gain is limited by the speed of the actuator, as shown by reference number 260 on curve 250. Such a limiting effect prevents complete compensation for the non-constant inner servo loop gain, as discussed below with respect to FIG. 16, which depicts the total gain 2 in region B.

For speed ratio errors in region A, the outer servo loop gain varies as a sole function of speed ratio as in the first embodiment, thus 1. The outer loop gain in region A is depicted in FIG. 11 as a constant function of speed ratio error. FIG. 12 depicts the outer loop gain as a function of speed ratio for area A according to a second embodiment of the present invention, step 7 seconds. Similar to the outer loop gain of the first embodiment of the invention.

The outer loop gain, depicted in FIG. 12, is inversely related to the inner loop gain, and its magnitude is such that the overall gain due to the ratio 7 seconds is equal to the desired overall gain of 0.08 ratio/second, depicted in FIG. The gain is chosen relative to the magnitude of the inner loop gain to correspond to the gain.

FIG. 13 plots the overall gain as a function of speed ratio error in regions A and B according to a second embodiment of the present invention at a ratio of 7 seconds. Similar to FIG. 11, a dashed line 200' separates the Craftsman and Area B speed ratio errors. In region A, the outer loop gain varies only as a function of speed ratio (as a function of speed ratio), and the plot of the
The embodiment is essentially similar to that shown in FIG.

Due to the limiting effect of the ratio actuator as described above with respect to FIG. 11, the outer loop gain in FIG. 13 is plotted as a family of curves according to speed ratio. 1.5'ORP M
, /RPM, the non-constant inner loop gain is fully compensated and the total gain is substantially the same as the desired total gain depicted in FIG. 0.
For lower numerical speed ratios such as 64 RP rt / RP M, if the loop gain is relatively high and the ratio actuator speed is limited, then
The overall gain may not correspond to the desired overall gain depicted in FIG.

Although faster actuators may be used to fully compensate for non-constant inner servo loop gain, the overall gain for lower numerical speed ratios may be used.

Faster actuators are inherently less accurate.

Therefore, the discrepancy between the actual and desired overall gain for low numerical speed ratios is a factor that must be tolerated to obtain the accuracy required for stability.

14 and 15 are flowcharts for implementing the m-control scheme of the present invention in a microprocessor-based controller such as that shown in FIGS. 1 and 2.

The flowchart in Figure 14A shows the main program loop, and the flowchart in Figure 14B shows the main program loop.
Represents an interrupt program for a program loop. As will be understood by those skilled in the art, MPU 120 typically executes the main loop's program instructions, but such execution is halted when the interrupt input of MPU 120 is reduced to a logic zero voltage level.

At this time, the MPU 120 executes the program command of the interrupt program instead. Following execution of the interrupt program, the l\4PIJ120 interrupts the main program at the interrupt point.
Resume program execution. Similarly, 1 by a person skilled in the art
As can be seen, interrupt 1 is in the main loop.
Appropriate program commands may be employed to inhibit or shield No. 8 or to allow interrupt signals.

As shown in Figure 2, the output of timer 126 is connected to line 127.
It is connected to the interrupt input of the Ivf PU 120 via the Ivf PU 120. +,h P U 120 operates in communication with timer 126 via buses 130 and 162 to feed various digital numbers into the timer register and to start and stop decrementing it in accordance with the program instructions of the main and interrupt programs. When the count in the tie'X register decreases to zero.

Output line 127 is pulled to a logic zero voltage potential to interrupt execution of the main program and initiate interrupt program execution, assuming the interrupt signal is not shielded.

The flow chart depicted in FIGS. 14A and 14B is a program for implementing a second embodiment of the present invention in which the non-constant gain of the inner servo loop is compensated for over the entire range of speed ratio errors. Represents a step.

The flowchart commands enclosed within dashed box 400 in FIG. 14A represent portions of the flowchart specific to the second embodiment. The corresponding flowchart portion for the first implementation column is depicted in dashed box 400' in FIG.

This should replace the instructions in the hox 400 of FIG. 14A if the first embodiment is adopted.

Referring now to FIG. 14A in more detail.

Start block 410 specifies a series of program instructions to be executed each time power is applied to the system. As will be understood by those skilled in the art, this block represents program instructions for initializing various input and control variables. After executing the start command.

MPU 120 does not read the value of the input signal, as indicated by block 420. As mentioned earlier.

These input signals include engine output speed 1.J, transmission input speed N, transmission output speed tag, and throttle position signal %T.
and manual selector position signals. Transmission input speed N
□ and output speed 1q, 1jPU 120 calculates the actual transmission speed ratio (No/
Calculate N□). Next, the MPU 120
Determine the desired speed ratio value as shown at 40. here,
It will be appreciated by those skilled in the art that the desired ratio value may be stored in an electronic lookup table (not shown) as a function of throttle position and transmission output speed; By addressing with a particular throttle position and transmission output speed value, the speed ratio error is then determined by distinguishing between the actual speed ratio value and the desired speed ratio value, as shown in command block 450. Then, in response to the speed ratio error mark, M-, P, U 120 is used to specify the correction movement direction to the step motor actuator 98.

A digital signal is output to step motor driver 160 via line 162 as shown in command block 460 .

According to a second embodiment of the present invention, 1viPO 120 then executes the command block 470 as shown in command block 470.

Determine whether the speed ratio error is outside a round band of ratio errors centered around zero error. The term dead band is used herein in its generally accepted meaning;
Speed ratio error size is O, Q I RP M / RP
It serves to prevent corrective operation of the transmission ratio unit when the ratio is less than a predetermined low value such as M. If the ratio error is within the round band, the abort input of lvi P U 120 is masked to prevent execution of the abort program, as shown in command block 510. If the ratio error is outside the dead band, the MPU 120 activates the step motor actuator 98.
The step rate is determined as a function of the speed ratio error and the actual speed ratio and the step rate is stored in a storage register (RFO1''()) as shown in block 480.

Representative step rates for actuator 98 according to a second embodiment of the present invention are depicted herein in FIGS. 11 and 12.

Such step rates may be stored in an addressable electronic look-up table as a function of the speed ratio error and the actual speed ratio, in duplicate for a desired speed ratio. To facilitate implementation of a desired step rate, the step rate values stored in the lookup table actually represent the time between actuator steps. Thus, large step rate values will result in a slow ratio change rate, and small step rate values will result in a fast ratio change rate.

After determining the appropriate step rate, the MPU 120 interrupt input can allow execution of the interrupt program as shown in command block 52[). Then M
P U 120 determines whether this is the first time since the initial power-up that the main program has been executed, as shown in decision block 5-0.

It will be appreciated that the answer to such a question may be determined by checking the state of a flag or other storage location that is initialized by the start command 410 and then changes value. The first time the main program is executed following application of power to the system, decision block 530
is answered in the affirmative, and the MPU 120 executes the command block 540.
As shown in <, load the step rate stored in REGR into type 126. MPU 120 then begins decrementing timer 126 as shown in command block 550.

After the first execution of the main program loop, decision block 530 is answered in the negative and command blocks 540 and 550 are skipped as indicated by approach yard line 555.

Command block 570 generally commands clutch actuator 110 .
Clutch lubrication pump 112 and transmission pressure regulating valve 10
It specifies further control functions to be performed by 1APU 12D, such as energizing 1APU 12D. Since such functions are not directly related to the control system of the present invention, they will not be described in detail. After executing such commands, MPU 120 returns to command block 420 as indicated by flow line 575.

Referring in more detail to the interrupt flowchart depicted in Figure K114B below, command block 580 commands stepper motor driver 160 via line 162 from PIAl 22 to cause output shaft 196 of stepper motor actuator 98 to move one step. Specify the program commands to issue commands to. The direction signal, previously described with respect to command block 460, determines the direction in which pressure should be compensated. After moving the output shaft 96,
P U 120 loads the output register of timer 126 with the contents of REGR as shown in command block 5.90. In this way, when the digital number in the timer output register decreases to zero, the timer will then cause the interrupt signal to move the actuator output shaft 96 one more step.

The Ivi P U 120 then returns to the main program and begins executing program commands at the interrupt point, as indicated by command block 600.

Next, the operation of the control system of the present invention is illustrated in FIGS. 14A and 14B.
This will be explained using figures. As can be seen from this description, the main program determines step rate values for the step actuator as a function of various input signals and
It serves to store the most recent step rate value. The interrupt program serves to move actuator output shaft 96 one step and refresh the output register of timer 126 at the step rate stored in REOR.

System power is first applied to the start block 410.
After the input and control variables have been initialized according to the program instructions in .

MPU 120 determines speed ratio errors for various input values. A digital output signal corresponding to the sign of the gear speed ratio error and indicating the correction direction for the stepper motor actuator 98 is then passed through one of the lines 162 to the stepper motor driver 1.
60. This output does not act to energize actuator 98, but only to select the direction of corrective action.

If the ratio error is within the ratio error dead band, no corrective action is required and the 9 interrupt input is masked to prevent execution of the interrupt program. As long as the interrupt input is shielded,
MPU 120 ignores signals applied to its interrupt input. If the ratio error is outside the dead band, a speed ratio corrective action is required, and the MPU 12.0 determines the appropriate step rate according to the speed ratio error and the speed ratio. In addition, one interrupt input will be able to allow execution of an interrupt program when an appropriate voltage potential is applied to the interrupt input. Only when the interrupt input is able to allow ratio correction will the timer 1260 output register be loaded with the last determined step rate and timer 126 can begin to decrease this rate. This step is only necessary after the main program loop has passed, after the timer 126 registers have been refreshed, usually by an interrupt program. When the step rate, which represents the time between steps, decreases to zero, timer 126 generates an interrupt signal, which causes MPU 120 to begin executing the interrupt program. In addition to moving actuator 98 one step and changing the speed ratio, the abort program also places a new step rate value from register R into timer 126. Operation of control 65 continues in the manner described above until the system becomes inactive.

The flowchart of FIG. 15 represents program instructions that should be substituted for the program instructions of FIG. 14A surrounded by box 400. Therefore.

The program instructions illustrated in the flowchart of FIG. 15 begin following execution of decision block 470 if the ratio error is outside the dead band. At this point, MPU 120 determines that the ratio error is determined by decision block 610 to be less than 0.10 RP I
vi/RP 111.

The standard value of 0.10 RP) and i/RPM divides the speed ratio error into regions A and 1 for speed ratio errors lower than 0.1ORPM/RPM, and region B for speed ratios larger than ORPMM/RPM. This is the reference value established for FIG. 6 for separation. The response speed for which decision block 610 answers in the affirmative is within region B, which is the primary control target. In this case, MPU 120 determines the step rate as a function of speed ratio error, as shown in command block 620. The ratio error table shown in command block 620 is preferably an electronic lookup table in which previously stored step rate values are recovered as a function of the address determined by the speed ratio error. If decision block 610 is answered in the negative, the speed ratio error is in region A where a stable response is the primary control target.
It's within. Therefore, MPU 120 determines the step rate strictly according to the actual speed ratio as shown in command block 630. Similar to the ratio error table shown in command block 620, the ratio table shown in command block 6O preferably allows previously stored step rate values to be recovered using addresses determined by the speed ratio. There is an electronic lookup display. Following execution of command block 620 or 650, MPU 120 stores a step rate value in gRE()R as shown in command block 640. At this point, proceed to execute the program instructions indicated in box 400'. The operations in implementing the first embodiment of the invention are essentially the same as in the second embodiment, except for the manner in which the step rate value is determined. In either embodiment, the step rate value for the speed ratio error in region A is determined as a unique function of the actual speed ratio. According to the second embodiment.

The step rate value for the speed ratio error in region B is determined according to both the actual speed ratio and the speed ratio error. According to a first embodiment, the step rate value for the speed ratio error in region B is determined as a sole function of the speed ratio error.

In summary, the present invention provides a new and improved outer servo loop for a continuously variable ratio transmission in which the gain of the servo loop is a non-constant function of the speed ratio provided by the speed maker. This provides an advantageous ratio control system. According to the present invention, the compromise between a stable ratio control response and a fast ratio control response characteristic of conventional methods is such that below that level, the stable response is the primary control target, and above that, the fast response is the primary control target. This can be avoided by establishing a reference speed ratio error that is . For ratio errors that require a stable response, the outer servo loop gain is determined relative to the inner servo loop gain to compensate the overall ratio control gain for the non-constant nature of the inner servo loop. Such control establishes a substantially constant overall ratio 101'' control gain regardless of the actual speed ratio provided by the transmission.

This gain will yield the desired stable response.

selected. For ratio errors that require fast response,
According to a first embodiment, the outer servo loop gain is determined as a sole function of the speed ratio error, and according to a second embodiment, the outer servo loop gain is determined as a function of the speed ratio error divided by seven. Both the first and second embodiments of the present invention produce the desired fast response. The first embodiment compensates for the non-constant nature of the inner loop gain only for ratio errors that require a stable response, and the second embodiment compensates for the non-constant nature of the inner loop gain for all ratio errors that require correction. compensate for the non-bipedal nature of. In essence, the outer loop gain is not fixed but variable and is controlled as a function of the actual speed ratio and speed ratio error to satisfy a predetermined control objective.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an automobile drive train and a control section for implementing the ratio control method of the present invention. Fig. 2 is a more detailed system diagram of the transmission and 1h() shown in Fig. 1. Fig. 6 is a control system diagram for the ratio control system of the present invention. Fig. 4 is a transmission speed ratio An experimentally obtained graph showing the actuator position vs. (＾°J). Figure 5 is a graph depicting the inner loop gain vs. speed ratio. Figure 6 is the desired speed ratio change rate (total gain) vs. speed ratio. A graph depicting the error. Figure 7 is a graph depicting the outer loop gain versus the actual speed ratio in the slow (stable) mode of operation for the first embodiment of the present invention. Figure 8 is a graph depicting the overall gain versus the present invention. FIG. 9 is a graph depicting the speed ratio in the slow or steady mode of operation for the first embodiment. FIG. 9 is a graph depicting the outer loop gain versus speed ratio error for the first embodiment of the present invention. FIG. 10 is the overall gain. 11 is a graph depicting the speed ratio error in the fast response operation f-do in the first embodiment of the present invention, with a group of curves based on the speed ratio. FIG. 11 is a graph showing the outer loop gain versus the present invention FIG. 12 is a graph depicting the speed ratio error in a second embodiment of the present invention. A graph is given of a family of curves based on the speed ratio. 7 FIG. Figure 13 is a graph depicting the overall gain versus speed ratio error for a second embodiment of the invention, giving a group of curves based on the speed ratio. and FIG. 14B are flowcharts for implementing the second embodiment of the invention on a programmed microprocessor. FIG. 15 is a flowchart for implementing the first embodiment of the invention on a programmed microprocessor. and the fourteenth
This is a flowchart for use in conjunction with the flowchart in Figure B. [Explanation of matrix of main parts] 16......Transmission 65...
......Control section 98...
. . . Actuation unit set 120 . . . Means for determining ratio error 160 . . . Drive circuit 170 . . .・・Inward rotation】Servo roof 0172・・・・・Outside servo loop Applicant: General Motors Corporation

Claims (1)

Claims: 1. An inner servo loop for adjusting the transmission speed ratio according to the position of the actuating member; and an inner servo loop for adjusting the position of the actuating member to establish a desired speed ratio in the transmission. an outer servo loop and means (120, 160) for determining a ratio error according to the difference between the actual speed ratio and the desired speed ratio and means (120, 160) for adjusting the actuating member in a direction that reduces such ratio error. In a continuously variable ratio transmission control system having a device for actuating an outer servo loop, the response of the inner loop is such that the rate of change of the speed ratio with respect to actuating member position is a non-constant function of the actual speed ratio. , when the ratio error is at or above a predetermined value, both rate adjusting means (120, 160) control the actuator so that the rate of change in the position of the actuator member with respect to time is directly equal to the IA number of the ratio error. adjusting the rate of adjustment of A to relatively quickly reduce the error to the predetermined value below which further adjustment would compromise the stability of the system in view of the non-constant response of the inner servo loop; provides an overall system response with a more satisfactory sense of transition, and furthermore, when the ratio error is less than the predetermined value, the rate adjusting means is such that the rate of change in the position of the actuating member with respect to time is a non-constant function of the actual speed ratio. and adjusting the rate of adjustment of the actuating member so as to be inversely related to the non-constant function of the inner loop, resulting in a substantially constant rate of change of the speed ratio with respect to time for all actual speed ratio values. A continuously variable bore transmission control system characterized in that the error is reduced relatively slowly so that the actual speed ratio corresponds to the desired speed ratio in a stable manner. 2. In the damping system according to claim 2, the adjustment rate of one actuating member is a first guaranteeable operation in which the rate of change of the actuating member position with respect to time is a direct function of the ratio error: E- either the rate of change of the actuating member position with respect to time is a constant function of the actual speed ratio and the inner loop non-linear stable and consistent by adjusting according to a second guaranteed mode of operation that is inversely related to the constant response, resulting in a nearly constant rate of change of the speed ratio with respect to time for all actual speed ratio values. The first or second operating mode is guaranteed to reduce the ratio error below a given error value when the magnitude of the ratio error is equal to or greater than a predetermined error value. Further adjustment is such that the non-constant response of the inner servo loop is reduced to said predetermined value such that the stability of the irrigation system is compromised. Also, when the ratio error is less than the predetermined value, a second operating mode is ensured to reduce the remaining ratio error in a stable manner, thereby ensuring that the ratio control system has a relatively large ratio error. A continuously variable ratio transmission control system characterized in that it is operated to provide a stable response when ratio errors are relatively small without sacrificing response speed. 6. In the control system as claimed in claim 1 or 2, the means for adjusting one actuating member adjusts the actuating member in a direction that reduces the ratio error when the ratio error exceeds a dead band ratio error value. above which the primary controlled object achieves a response speed with a satisfactory sense of progression, and below which the primary controlled object achieves a stable response speed with a minimum excursion of the actual speed ratio with respect to the desired speed ratio. It consists in achieving a response. Means are provided effective for establishing a predetermined ratio error value that substantially exceeds a deadband ratio error value, the first means being effective in establishing a ratio error value with respect to time when the ratio error is at or above said predetermined ratio error value. Actuating member position σ) Establish an outer loop response function such that the summerization rate varies in direct relation to the ratio error, and the rate of change of the velocity ratio for 9 hours is satisfied 1
The second means is to provide an overall response function so as to achieve the primary objective of response speed with a sense of transition, and when the ratio error is less than the predetermined value, the rate of change of the actuating member position with respect to time is equal to the actual speed ratio. , and such a relationship is inverse with respect to the inner loop response function such that the rate of change of the speed ratio with respect to one hour is approximately equal to that for all actual speed ratios. Continuously variable ratio transmission control system characterized in that it provides a constant overall response function to achieve the primary objective of a stable response with a minimum excess of the actual speed ratio with respect to the desired speed ratio. . 4. In the control system according to claim 1 or 2, the transmission σ) input shaft is driven toward the actual speed ratio and the desired speed ratio to reduce the θ) ratio error between the two. The device for controlling the speed ratio between the output shaft and the output shaft adjusts the actual speed according to the position of the actuating member such that the rate of change of the speed ratio with respect to the actuating member position is related to the speed ratio by a non-constant inner loop gain function. means including an inner servo loop for determining the ratio, and a means for determining the ratio, except when the ratio error is sufficiently small, when there is a risk that the system will become unstable with the actual speed ratio exceeding the desired speed ratio. means including an outer servo loop for adjusting the position of the actuating member in accordance with a fast response mode of operation when the adjustment is made in accordance with a stable mode of operation; Compare the actual speed ratio toward the desired speed ratio with respect to the overall rate of change of the speed ratio with respect to time, which is the rate of change in the position of and acts in conjunction with the first range of rate values to give the desired sense of transition. The first to drive rapidly
means for controlling, over a first range of rate values, the rate of change determined by the relationship between the ratio error and the actual speed ratio by an outer loop gain function of jμm1, and operation with respect to time in a stable responsive mode of operation. The rate of change in the position of the member is −
This rate of change is approximately the inverse of the non-constant inner-loop gain function and acts with the non-constant inner-loop gain function to change the actual speed ratio over the speed ratio range to give repeatability of the system. the overall rate of change of the speed ratio with respect to time that is approximately constant over time and sufficiently low to provide stability of the system by preventing the actual speed ratio from exceeding the desired speed ratio; for controlling the rate of change determined in relation to the speed ratio by a second outer loop gain function that is driven relatively slowly toward the second range of rate values over a second range of rate values that is generally lower than the first range of rate values; A continuously variable single-speed transmission control system for an automobile, characterized in that it comprises means.